Brian to be a geometry teacher v the Teach for America program and started the geometry routine at his school




You are watching: Which undefined term is needed to define an angle?

In Geometry, we have actually several undefined terms: point, line and also plane. Indigenous these three undefined terms, all other terms in Geometry deserve to be defined. In Geometry, we specify a allude as a location and no size. A line is characterized as something that extends infinitely in one of two people direction however has no width and also is one dimensional when a aircraft extends infinitely in 2 dimensions.


There are three undefined state in geometry. From these terms we specify everything else. The first term is point. The second term is plane. And the 3rd undefined term is the line. Therefore let's go earlier and define these as much as us can. Currently we're no really defining point, we're just describing it. A allude has no size; it only has a location. And the method that we label it is v a resources letter. So us can call this allude P. A aircraft is a level surface that has no thickness, and also it will expand infinitely in every direction.So one means to visualize what a aircraft could it is in is come think about a sheet of paper. Or if there space two differences between a sheet of record and a plane, the first is this record does not extend in every direction. Secondly, this document actually has some thickness and a aircraft will not. Now you deserve to name a airplane using a solitary capital letter, usually written in cursive, or by three non-collinear points. And also collinear we'll talk around in a 2nd here, but collinear method they're no on the very same line. So let's say you had a allude right here: allude A, allude B, and point C. You could contact this plane, aircraft ABC. Meaning of coplanar: We actually can define this, is points, lines, or anything, segments, polygons in the same plane. So two things space coplanar if lock are, as with we have actually in the photo here, in the very same plane. Therefore "co", you can think the it together a word for sharing. For this reason you can think that coplanar together sharing the same plane. Currently the third undefined ax is a line. And a heat is collection of point out or, words that you could learn later on is locus, prolonging in either direction infinitely. Therefore a line is going to be all the points, and we deserve to actually choose two of them to name it. So us can contact this heat AB. Now when you're labeling a line, it's vital to include at least two points. Or if you have actually some sort of smaller letter over here, we can contact this heat L. But an alert how I'm composing the arrows over my letters; I have actually arrows on either side. And also these arrows tell you, the geometry student, that it expand infinitely in this direction. Now this arrowhead here extend infinitely in the direction. You can have points it is in collinear, that is, they share the very same line. So right here we can have, C, D, and E are all collinear. And also if friend look at point F here, I attracted this in to attract a contrast. You have the right to see that allude F is no on this line, therefore F is no collinear through C, D, and E. However I could say that E is collinear through C and D, D is collinear through C and also E, and C is collinear v D and E.

See more: What Are The First Three Words Of The Bible? ? Question: First Three Words In The Bible

Therefore the three key terms that space not definable, however only describable, space the line, i m sorry is a collection of points expanding infinitely in one or the other direction; plane, i m sorry is a level surface with no thickness; and the third undefined hatchet is point and that has a location and also no size.